docs: def save(self, filepath):
          """
          Saves the classifier to `filepath`.
          Because this classifier needs to save the dataset, it must
          be something that can be pickled and not something like an
          iterator.
          """
  
          if not filepath or not isinstance(filepath, str):
              raise ValueError("Invalid filepath")
  
          with open(filepath, "wb") as filehandler:
              pickle.dump(self, filehandler)